Process for the refining of pig iron in other than round vessels



United States Patent 3 098,740 PROCESS FOR THE PiEFlNING 0F PIG IRQN IN OTHER THAN RQUND VESSELS Paul Ernst Hardt, Hagen-Haspe, Germany, assignor to Ilockner-Werke A.G., Duisburg, Germany, a corporation of Germany Noprawing. Filed Aug. 1, 1960, Ser. No. 46,342 Claims priority, application Germany Aug. 7, 1959 2 Claims. (Cl. 75-60) The invention relates to a process for the refining of pig iron by blowing oxygen onto a metal bath under intense agitation of the substance of the bath in a refining vessel rotating about its longitudinal axis.

It has been found that when formed in a non-round furnace vessel, say, an elliptical vessel, assuming such a vessel to exhibit an adequately great departure from round shape, and assuming a correspondingly ample supply of refining gas, the process can be appreciably accelerated. The refining rates capable of achievement in such an event are equal to those obtained for acid or basic converters where the blast is delivered from the bottom. The refining in rotary, non-round refining vessels thus afiords an acceleration of the refining process, as compared with other oxygen refining processes, particularly such as are conducted in similarly rotating, cylindrical refining vessels.

It has been found that other oxidation conditions being equal, startling and unanticipated results are obtained by shifting from round to non-round vessels. Thus, for instance, given identical refining supply and an identical speed, the decarburization rate is nearly doubled where work is performed on the one hand with round refining vessels rotating about their longitudinal axis and then again with non-round vessels of the same kind. This boost of the rate of reaction, brought on primarily by the thorough mixing of the bath and the slag and by the faster rate of oxygen absorption on account of the increased surface, is so great that a reduction of the metallic and nonmetallic oxides from the slag is observed when certain speeds governed by the axis ratio of the non-round refining vessels is exceeded. Where the reduction of metal oxides such as iron oxide or manganese oxide is concerned, this process is particularly advantageous inasmuch as it reduces the metal losses, While enhancing the yield. Where, however, oxides such as phosphoric acid, associated with detrimental foreign substances are concerned, their reduction leads to an undesirable migration of the phosphorus back to the smelting bath.

The invention seeks to exploit the advantages derived from operating with non-round refining vessels, without thereby being obliged to incur the disadvantages which are apt to arise along with it. The invention thus pro vides hitherto unknown directives of great precision, which brings with it a marked increase in production for the refining process, while at the same time affording a metallurgically meticulous method of performance. It has been taken as a point of depantune that the process is universally applicable, that is suited for employment for any available type of pig iron. Such a process must therefore also take into account the special metallurgical requirements for dephosphorization. The invention is predicated on the finding that where refining is carried out by blasting of an oxygen supply into other than round refining vessels which rotate about their longitudinal axis, it is essential to adhere to an optimal range of speeds such speeds being governed by the axis ratio.

3,098,740 Patented July 23, 1963 The invention is characterized in that a rate of rotation ranging from 16 to 34 revolutions per minute is maintained for non-round refining vessels which rotate about their longitudinal axis, tor an axis ratio from 1:2 to 1:5, and the rate of oxygen feed being from 4 to 10 Nm. of oxygen per minute and per ton of pig iron and at a relatively low pressure, in the neighborhood of 6 atmospheres. It has furthermore been found that a relatively narrow range of speeds needs be maintained as a function of the axis ratio for the speediest possible dephosphorization, the latter being required even in the case of phosphorus poor pig iron. This optimal rate of rotation for an axis ratio of 1:2 is from 18 to 20 revolutions per minute, while for an axis ratio of 1:5 it ranges from 16 to 18 revolutions per minute. As a normal metallurgical procedure, dephosphoriZa-tion takes place first and is followed by decarburization.

Pursuant to a further improvement of the invention, during the first part of the refining process, the duration of which is governed by the phosphorus content of the pig iron and other conditions being equal, the speed is from 16 to 20 revolutions per minute, whereas during the second part of the refining process, the object of which is decarburization, the rate is from 20 to 34 revolutions per minute.

This application is a continuation-in-part application of my earlier filed application Serial No. 753,765, filed August 7, 1958, now Patent 3,034,885, issued May 15, 1962.

What I claim is:

1. A process for the refining of pig iron comprising: providing a non-round refining vessel having a minor axis to major axi ratio of from 1:2 to 1:5, charging the vessel with material to be refined, rotating the refining vessel about its longitudinal axis at a speed lying in the range of 16 to 34 revolutions per minute and supplying oxygen to the vessel at a pressure of about 6 atmospheres and at a rate between 4 to 10 Nm. per minute per ton of pig iron.

2. In a process for refining pig iron in an elliptical refining vessel having minor to major axis ratio of from 1 :2 to 1:5 which comprises charging the vessel with material to be refined, rotating said vessel at a rate of speed lying in the range of from 16 to 20 revolutions per minute, supplying oxygen to the vessel at a relatively low pressure and at a rate between 4 to 10 N-m. per minute per ton of pig iron for dephosphorizing the pig iron, the duration of which is governed by the initial phosphorous content of the pig iron and then rotating said vessel at a relatively higher rate lying in the range of from 20 to 34 revolutions per minute to effect decarburization of the pig iron.

References Cited in the file of this patent UNITED STATES PATENTS 879,480 Von .Maltitz Feb. 18, 1908 2,151,360 Tafel Mar. 21, 1939 2,258,850 Eulenstein et al. Oct. 14, 1941 2,598,393 Kalling et al. May 27, 1952 2,668,759 Tenenbaum Feb. 9, 1954 2,693,411 Cremer Nov. 2, 1954 2,817,584 Kootz et al. Dec. 24, 1957 2,853,377 Kalling et al. Sept. 23, 1958 3,034,885 Hardt May 15, 1962 FOREIGN PATENTS 570,169 Belgium Aug. 30, 1958 

1. A PROCESS FOR THE REFINING OF PIG IRON COMPRISING: PROVIDING A NON-ROUND REFINING VESSEL HAVING A MINOR AXIS TO MAJOR AXIS RATIO OF FROM 1:2 TO 1:5, CHARGING THE VESSEL WITH MATERIAL TO BE REFINED, ROTATING THE REFINING VESSEL ABOUT ITS LONGITUDINAL AXIS AT A SPEED LYING IN THE RANGE OF 16 TO 34 REVOLUTIONS PER MINUTE AND SUPPLYING OXYGEN TO THE VESSEL AT A PRESSURE OF ABOUT 6 ATMOSPHERES AND AT A RATE BETWEEN 4 TO 10 NM.3 PER MINUTE PER TON OF PIG IRON. 